Hull structure concepts on internal audits and inspections

During HSSEQ ISM ISPS Audits, internal auditors shall verify, among others, the compliance with the objective of the Code: (ISM Code 1.2.1) “The objectives of the Code are to ensure safety at sea, prevention of human injury or loss of life, and avoidance of damage to environment, in particular to the marine environment and to property”, this mean that internal auditor must be aware about (ISM Code “applicable codes, guidelines and standards recommended by the Organization, Administrations, classification societies, and maritime industry organizations are taken into account”.  During a condition survey or pre-purchase inspection, the good knowledge of these concepts is conclusive.

 In order to fulfil this, marine auditors, marine surveyors and inspectors shall be familiar with several standards, rules and regulations, but they should be familiar with specific hull structure concepts as well.  Many internal auditors and marine surveyors or inspectors are qualified as master mariners, chief mates, marine mechanical engineer, naval architects, and this should be enough to become them familiar with, and indeed they are, but many of them are well familiar on the basis of mother language concept.

 This guideline has been prepared in order to provide standardization of concepts into the English language and to be useful for providing technical words and concepts to make good internal audit reports and good condition inspection reports.

 Hull: The hull is the main body of the ship

Shell plating: are the sides of the hull.

Main Deck: It is the uppermost deck running continuously from bow to stern.

Bilge: It is the intersection of side plating and bottom plating.

Keel: The keel is a member, or series of members, running longitudinally that forms the structural base of a ship. It is a ship’s centre line providing longitudinal strength and efficiently distributes local stresses when the ship is dry docked. Two types of keels are used to build ships of a certain size: the flat keel and the duct keel.

Girders: A girder is a longitudinal member used in the construction of the bottom of a ship. They can be solid or not and can be placed above the keel (centre girder) or spaced equal distances from it (side girders). They can be continuous or divided by floor sections (intercostal side girders). The centre girder is always one continuous piece and must be fastened to the keel with a continuous weld. Girders must extend as far as possible from the forward to the aft end of a ship.

Floors: These are made up of cross members that are mounted perpendicular to the keel and girders. There are three main types of floor: solid, plate and bracket.

Frames: Fastened to the keel, running athwart ships. Support the skin and divide ship into vertical rows of compartments. Frame type and spacing vary considerably depending on the ship’s construction.

Deck beams: These are transverse members that connect the top ends of the frames, forming the transverse framing for the deck.

Deck girders: These are longitudinal members that combine with the beams to form the longitudinal framing of the deck.

Longitudinals: A very general term to identify any small longitudinal member that can be used for several purposes. This term is used more specifically in longitudinal framing.

Web frames: Oversized members that replace a frame at certain locations on a ship.

Bracket: A general term that identifies any part used to connect two members.

Beam knee: Bracket located at the end of deck beams that connect the beam and frame to the shell plating.

Pillar: Vertical member inside a ship that connects the deck to the ship’s bottom, where it is installed between two tween decks, especially around hatches. They are quite bulky and complicate cargo handling inside holds.

Plating: The plating of a hull is the series of plates that form the watertight shell of the hull. There is bottom plating, deck plating and side shell plating.

Bilge plating: Longitudinal plating that connects the side shell plating to the bottom plating.

Tank top: Watertight series of plates attached to a ship’s bottom framework.

Double bottom: The double bottom is the watertight space between the bottom plating and the tank top. Its height varies according to the size and type of ship, but it is generally between 0.75 and 1.5 metres. A double bottom is divided into several watertight compartments by watertight floors and girders. These compartments can be used to store fuel, oil and ballast water. They are often used to adjust a ship’s list and trim.

A double bottom maintains a ship’s watertight integrity when the bottom is damaged. The tank top greatly increases a ship’s longitudinal strength and forms a platform to carry the ship’s cargo and machinery.

Weatherdecks: The portion of the main deck and the upper levels exposed to the weather.

Bulkheads: “Walls” aboard ship.

Overheads: “Ceilings” aboard ship.

Compartments: “Rooms” aboard ship. Bounded by overheads, bulkheads and decks.

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